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Fundamentals of Human Nutrition/Defining Nutrition

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Nutrition is the science that interprets the interaction of nutrients and other substances in food in relation to maintenance, growth, reproduction, health and disease of an organism. It includes food intake, absorption, assimilation, biosynthesis, catabolism and excretion (2014).Closing </ref> missing for <ref> tag It is important to make a habit of healthy eating. The more often you eat healthy, the easier it will be and the more you will start to enjoy healthy foods over un-healthy foods. It can be difficult sometimes to choose an apple over a candy bar and you don't always have to, but in the long run, your body will thank you for eating healthy. We often don't think about the nutritional content of our food, but do some research and find out what you're really putting in your body when you eat certain foods. Awareness of the contents of our consumption is the first step in moving towards a healthier diet and therefore a healthier body.

According to Marriam-Webster dictionary, malnutrition is defined as "lack of proper nutrition, caused by not having enough to eat, not eating enough of the right things, or being unable to use the food that one does eat". At first thought, it is easy to think of malnutrition as only not having enough food however as the definition so evidently points out, it also incorporates not eating enough of the right things for your body or if your body is unable to use the food you are ingesting for what it needs. It is extremely important to eat a well balanced diet in order to stay in healthy standing as well as giving your body the nutrients it needs to sustain your active life.

There are a number of causes of malnutrition. It may result from an inadequate or unbalanced diet, problems with digestion or absorption, certain medical conditions. Malnutrition can occur if you do not eat enough food. Starvation is a form of malnutrition. You may develop malnutrition if you lack of a single vitamin in the diet. In some cases, malnutrition is very mild and causes no symptoms. However, sometimes it can be so severe that the damage done to the body is permanent, even though you survive. Malnutrition continues to be a significant problem all over the world, especially among children. Poverty, natural disasters, political problems, and war all contribute to conditions—even epidemics—of malnutrition and starvation. A study conducted by Action Against Hunger-USA (ACF-USA) among children under five in the Nuer community of Old Fangak, central Upper Nile, found that most of the malnourished children had been sick over an extended period, suffering from diarrhea, respiratory infections and fever, or a combination of several illnesses. Disease and inadequate food intake seemed to have particularly affected children under five years old, the report stated.

As the name macro suggests carbohydrate, protein, lipids,fats and water make up the bulk of the diet and signify the items the body requires to be consumed in large quantities. In addition, carbohydrate, protein and lipids are the body's main source of energy, with carbohydrate and protein providing 4 kcals/g (16.8 kJ/g) and lipids providing 9 kcals/g (37.8 kJ/g).Closing </ref> missing for <ref> tag This increases the body’s blood glucose levels.[1] The energy supplied by carbohydrate is of particular importance to the brain as the body's only carbohydrate-dependent organ.[2] This category also includes dietary fiber, which are either soluble or insoluble and offer several health benefits. Carbohydrates are divided into two categories: simple, which include items made up of 1 or 2 sugars, which increase the blood glucose level quickly and complex, which includes from 3 to >10 sugars and increase the bloods glucose levels more slowly. Typical sources are wheat, rice, potatoes, fruit, sugar beet and whole grains. Carbohydrates are an essential part of the diet and should not be restricted, choosing the complex variety is the healthiest option.[3]

Excessive consumption of refined sugar and simple carbohydrates can contribute to obesity and the onset of type 2 diabetes.[citation needed][4] Diabetes is dysfunction of the body’s ability to metabolize glucose due to insufficient levels or ineffective use of insulin.[5] Simple carbohydrates in food and drinks are also associated with increased risk of dental caries, (Mobley, Marshall, Milgrom, & Coldwell, 2010). Good start, what might excess sugar intake mean for other macronutrient and micro-nutrient intake?

Protein should make up 10-23% of the bodies intake for energy.[6] In addition to providing energy protein also assists with the regeneration and growth of cells, acquired by the consumption of 9 essential amino acids and 11 non-essential amino acids, which are synthesized in the body.[7] Typical sources of essential amino acids are meat, fish, eggs, dairy products and soya, which constitute complete proteins or combinations such as rice and lentils and peanut butter sandwiches.

Protein-energy malnutrition (PEM) is a group of protein deficiency disorders,[8] including marasmus, kwashiorkor and a combination condition marasmus-kwashiorkor. Marasmus is a wasting disease characterized by emaciation and is an adaptive response to starvation. Kwashiorkor in contrast, is characterized by a swollen belly, but is also a wasting disease and a mal-adaptive response to starvation.

The lipid macronutrient group is made up of fatty acids, triglycerides, phospholipids, and sterols. Lipids should make up 20-45% of the bodies energy intake.[9] In addition to providing energy lipids also assist the body with the absorption of fat-soluble vitamins.

Fatty Acids
Fatty acids are divided into three categories saturated, which is not essential to the body and monounsaturated and polyunsaturated. There are 2 essential fatty acids that the body can’t produce linoleic acid (omega 6) and linolenic acid (omega 3).[10] Excellent sources of essential fatty acids are fish and flax seed and canola oil.

Triglycerides
Triglycerides are a type of blood lipids. They are organic compounds composed of one glycerol and three fatty acid molecules. When the fatty acids combine with the alcohol glycerol, it is referred to as an ester. The body produces triglycerides in the liver, however they are also consumed as part of the diet. Triglycerides are present in both plant and animal food sources (AHA Staff, 2013). Plant sources of triglycerides include vegetable oils such as sunflower oil and peanut oil. The animal sources of triglycerides are present as solid forms in foods like meat products such as beef, or dairy products such as whole milk (Staff, 2015). Within the body, triglycerides function as an energy source like other types of lipids. However, triglycerides differ in that they primarily function as stored energy (Staff, 2013). When calories of any form, whether it be protein, carbohydrates, or fats, are consumed in excess, the body stores the extra energy in the form of triglycerides (Staff, 2015). Located in fat cells, triglycerides are stored until the body generates hormones to release the triglycerides for energy. Like cholesterol, triglycerides are hydrophobic and cannot be dissolved in the blood (Staff, 2015). For this reason, specialized transport proteins known as lipoproteins are responsible for circulating triglycerides throughout around the body through the bloodstream. Normal blood triglyceride levels are considered anything below 150 milligrams per deciliter of blood. High levels of triglycerides in the body are associated with a hardening of the arteries known as atherosclerosis, as well as other cardiac diseases (Staff, 2015)

Phospholipids

A phospholipid is a class of lipids that makes up a small minority of lipids found in the diet. They are commonly found fat-containing foods and oils. A phospholipid is made up of a glycerol with 3 attachment sites. Two of those attachment sites contains fatty acids and the third site contains a phosphate group. The two attached fatty acids are hydrophobic, thus making them insoluble in water, but soluble in fat. The attached phosphate group is hydrophilic allowing them to dissolve in water, but not in fat. Phospholipids are able to be synthesized in the body through chemical changes to triglycerides. As a result, phospholipids are not a dietary essential for the body. However, they are found naturally in foods. These hydrophobic tails and hydrophilic heads play a crucial role in the functions of phospholipids: As a component of cell membranes and as emulsifiers. A cell membrane is composed of phospholipids packed tightly together in a structure called a bilayer. In this bilayer, the hydrophobic fatty acid tails format themselves to make up the inner part of the bilayer as a source of protection from the intracellular and extracellular fluid surrounding the cell. The hydrophilic phosphate groups form "heads" that make up the outer half of the bilayer. This phospholipid bilayer allows the cellular membrane to be selectively permeable and assist fat soluble substances to enter or leave the cell.[11] Phospholipids as well act as an emulsifier, allowing fats to be mixed in blood and other body fluids. Lecithin is a common phospholipid used for its emulsifying abilities.[12]

Sterols

Sterols are a class of lipids with a hydrocarbon ring structure. They are derived from alcohol and contain a multiple ring structure, thus deriving the name "sterol". Cholesterol, for example, is made from a hydrocarbon ring structure. Cholesterol is the most common sterol typical sources are eggs and cheese. Other sources of cholesterol are meats, seafood, poultry, other dairy products and plant-derived foods. However, cholesterol derived from plant foods are a very insignificant amount compared to those derived from animal foods. Plant foods normally contain a different type of sterol structurally similar to cholesterol called “phytosterols”. These plant sterols interfere with cholesterol absorption in the intestine and can help in the reduction of blood cholesterol as a result.[13] The main function of sterols is as a precursor to other compounds found in the body. Cholesterol, for example, is used to synthesize vitamin D within the body. Other compounds include the bile acids, sex hormones, and adrenal hormones. Sterols also make-up part of the cellular membrane, serving a structural role.

Digestion and Absorption of Lipids

The digestion and absorption of lipids differs from that of both carbohydrates and proteins. Unlike the other nutrients, lipids are not water soluble and therefor require a more advanced process in order to be broken down and absorbed by the body (Bowen, 2015). Digestion of lipids begins in the mouth and stomach, however most of lipid digestion takes place in the small intestine (King, 2015). Bile, which is made in the liver, begins the digestion of lipids by physically breaking them down into smaller molecules. By doing so, it is easier for lipase to begin chemically breaking down lipids. Lipase is a pancreatic enzyme that is responsible for the digestion of lipids (Bowen, 2015). Lipase breaks the lipids down into free fatty acid and monoglyceride molecules to make absorption easier. Absorption of the digestive products occurs in the small intestine. The molecules left over from hydrolysis are absorbed into mucosal cells that line the walls of the intestines. Absorption occurs through either simple diffusion or with assistance from other transports (King, 2015).

High levels of lipids in the bloodstream, particularly LDL and triglycerides, can increase a person’s risk of developing coronary heart disease. Part of this is due to the fact that the body must create more capillaries in order to supply blood to excess fatty tissue. This causes the heart to work harder, increasing strain and thus the chances of developing disease.[14]

The condition of having consistently high lipid levels in the blood is known as hyperlipidemia, and it can lead to other health problems such as atherosclerosis (hardening of the arteries), heart disease, and stroke.[15] If left untreated, high lipid levels can lead to plaque accumulation on artery walls. Plaque is made up of lipids, such as fat and cholesterol, as well as calcium and other blood substances.[16] Oxidized lipids can increase the amount of calcium that is deposited on artery walls, constricting blood flow and increasing the chance of an interruption.[17] Small LDL particles are more likely to oxidize, and patients with large numbers of small LDL particles in their system have a higher risk of developing health complications, including diabetes.[18] Reduced arterial blood flow can also cause problems such as angina (chest pain) or even a heart attack. In cases of heart attack, blood flow is completely cut off from a section of the heart muscle, which can ultimately lead to serious complications or patient death if left untreated.[19]

Hyperlipidemia can be treated with therapeutic lifestyle changes, such as reducing the amount of dietary saturated fat and cholesterol and increasing intake of soluble fiber and plant sterols.[20]

High levels of LDL in the blood can be reduced with various treatments. Weight loss is often recommended, as the reduction of excess weight can lower levels of LDL. Additionally, foods derived from soybeans, such as tofu and various other meat replacements, contain a specific antioxidant compound that can help decrease LDL levels. In more extreme cases, however, a patient may be prescribed lipid-reducing medications, such as statins, fibrates, and compounds that prevent the body from reabsorbing the cholesterol found in bile acid. Niacin can also be used to help reduce LDL levels.[21]

High triglyceride levels in the body can also be an issue. Diabetic patients are more likely to have high triglyceride levels. This is partly due to the effects of insulin on lipid flux regulation.[22] Triglyceride levels can be lowered by eating foods high in omega-3 fatty acids, such as cold-water fish like salmon and sardines.[23]

In contrast with LDL and triglycerides, high levels of HDL can actually lower the chances of developing heart disease.[24] Excess body weight and smoking are both known to lower HDL levels.[25]

Hypercholesterolemia
Excessive cholesterol in the blood can lead to coronary heart disease and disease of the arteries. Of major concern is when blood levels are high in LDL cholesterol and trigylcerides, and low levels of HDL cholesterol.[26]

Micronutrients are commonly known as vitamins and minerals. They are called micronutrients because the body only requires a very small quantity of vitamins and minerals to assist the body in its normal functions. These nutrients are essential to our bodies, however our bodies are unable to produce micronutrients and they must be sourced from our diets. To gain the essential nutrients we need it is important to eat a well balanced diet that includes a range of colorful fruit and vegetables, nuts and whole grains. That way we gain such vitamins as Vitamins C to aid the immune system, Vitamin E to help fight free radical damage, or minerals such as Iron for red cell production and Calcium for strong healthy bones.

The World Health Organisation calls micronutrients "the 'magic wands' that enable the body to product enzymes, hormones and other substances essential for proper growth and development". The International Atomic Energy Agency (IAEA)[27] has a program called 'Improving Nutrition through Nuclear Sciences', IAEA understands the essential role micronutrients play in our bodies and states "when micronutrients are not sufficient from food in the diet, significant health problems can result" and a significant amount of research has gone into understanding the physiological role and the health consequences of micronutrient deficiencies. Joint experts, the World Health Organisation and the Food and Agricultural Organisation of the United Nations conducted research in 1998 to establish clear parameters of defining micronutrients deficiencies for public health, as well as to develop preventative action and control strategies.[28]

There are a total of thirteen essential organic vitamins in the body which include Vitamin A,C,D,E,K,B1,B2,B3,B6,B12,pantothenic acid,biotin, and folic acid. These are used on a daily basis for tasks around your body you wouldn't even think of. Certain vitamins are used to see in dim light or make sex hormones and without them, we wouldn't function properly. Vitamins are unique in the fact that they denature by heat, light, and chemical agents. They need to be intact in order for them to work properly.

Fat Soluble Vitamins

The fat-soluble vitamins which mean they are soluble in lipids, include A,D,E, and K.[29] They are dissolved in fat before they are absorbed into the bloodstream where they reach the rest of the body and carry out many different functions. Consuming too many of these vitamins can actual increase the toxicity of your body and become dangerous. However these vitamins are essential and contribute to things such as your eye health, antioxidants to cancer, strong bones, blood clotting and lower risk of heart disease.

Water Soluble Vitamins

Water soluble vitamins are more easily dissolved in water compared to fat-soluble, and are constantly needing them to be replenished in our body since they are eliminated via urine. Therefore, we get a lot of these vitamins through our diet. Water-soluble vitamins include vitamin C as well as the vitamin B complex.[30] Something unique to water-soluble vitamins is the actual vitamins can be lost or destroyed if food isn't prepared properly. For example, keeping milk and grains in sunlight for an extended period of time can denature water-soluble vitamins.

Minerals are inorganic materials that are essential for different functions and growth in your body, however they do not give energy.[31][32] Although there are 16 essential minerals found in the human body, research is constantly trying to prove more exist and are essential. Among other functions, minerals contribute to bone and teeth production, immune health, nerve and muscle function and more. Unlike vitamins, minerals are inorganic so they are technically indestructible and do not need to be handled with such care as vitamins do. However, some minerals can bind to certain substances that make it difficult for the body to absorb them. The two types of minerals, major and trace, are described below.

Major Minerals

The major minerals include calcium, magnesium, phosphorus, potassium, chloride and sulfur. These are called "major" minerals. This is not because they are more important than trace minerals, but because they are needed in larger amounts than trace minerals. Major minerals contribute to processes such as proper fluid balance, healthy bones and teeth, nerve and muscle communication, and more.

Trace Minerals

Trace minerals include iron, copper, zinc, manganese, fluoride, selenium, and cobalt. As mentioned earlier, these minerals are not less important than the major minerals but the human body simply needs a lesser amount. Trace minerals contribute to red blood cell function, thyroid hormone production, are part of enzymes, regulate blood glucose, and many more.